New Opportunities in Metallization Integration in Cofired Electroceramic Multilayers by the Cold Sintering Process

Abstract

Metallization with high conductivities is critical in the design of high performance multilayer electroceramic devices. Cold sintering offers exciting new opportunities in the integration of different material classes; here we explore novel metal chemistries and demonstrate their integration into ceramic multilayers. The processing is enabled due to the cosintering of both the ceramic and metal powders in fast times and at extremely low sintering temperatures. Metal powders are printed as pastes and formed into multilayers that can be cosintered with the ceramic ZnO; these specific metals include Cu, Fe, and Al. The multilayer structures are assembled and fabricated under a thick film process and enabled by using a polypropylene carbonate binder system that can be removed at low temperatures under N 2 −H 2 forming gas, permitting control of oxidation of the Cu, Fe, and Al. As a result, extremely high conductivity electrodes are fabricated and quantified through the equivalent series resistance (ESR). In addition, new electrode composite concepts, such as mixed particles of Fe−Cu cosintered in between the ZnO layers, are possible with the cold sintering process.

A Route towards Fabrication of Functional Ceramic/Polymer Nanocomposite Devices Using the Cold Sintering Process

“…The integration of base metals such as Cu, Fe, Al, and Cu/Fe composite in the fabrication of multilayer systems, sintered at 260 °C by the CSP, were previously demonstrated by de Beauvoir et al. Herein, we implemented a similar methodology to fabricate a polymer (PEI) and ceramic-phase (ZnO) nanocomposite MLV with Cu as an inner electrode. To avoid the thermal degradation of the PEI polymer, which has a glass transition temperature of ∼225 °C and a decomposition temperature of ∼250 °C in air, processing temperatures were decreased to 220 and 120 °C in N 2 /H 2 mixture (Figure ).…”

“…Recently, Zhao et al presented a new type of nanocomposite structure consisting of ceramic (ZnO) and polymer phases (PTFEpolytetrafluoroethylene) that provide the characteristic varistor I – V behavior . Additionally, de Beauvoir et al exhibited applicability of the integration of metallization of different metal types ( i.e., Fe, Cu, and Al) into functional electroceramic with the cofiring process as a multilayer form by the enormously low sintering temperature that can be called as the “cold sintering cofired ceramic (CSCC)” process that is reported for the first time in the literature …”

Cold Sintering of Iron Powdered Metal Compacts and Their Performance

“…The CSP for ceramics utilizes an aqueous solution of powders to induce what is believed to be a dissolution-precipitation mechanism from hydrated powders via liquid phase sintering at particles boundaries. This results in densification at significantly lower temperatures than conventional sintering [1][2][3][4]. For the study discussed in this paper, the focus is on powder metal systems rather than ceramic systems.…”

Densification and Strengthening of Ferrous‐Based Powder Compacts Through Cold Sintering Aided Warm Compaction

“…[ 8 ] The process has also been extended to demonstrate the effect in metals that are used to make electrodes in multilayer ceramic passive components such as varistors and capacitors, and microwave filters. [ 9 ] In addition, the low temperatures have enabled new types of nanocomposites with modified grain boundaries and confined interfacial polymers and nanomaterials. Cold sintering in these applications has also enabled cosintering of high‐performance high conductivity inner electrodes of several metal chemistries with small particle sizes of ≈0.1 to 0.5 μm that include Ag, Cu, Ni, Fe, and Al.…”